In land development projects, it is often desirable to take samples to determine whether certain minerals or other valuable substances are present in the ground. To effect such sampling, drilling machines are commonly used by means of which tubes are driven into the ground such that a core of the ground material may be lifted to ground level to be examined. Drilling machines of this kind are expensive, and also heavy and difficult to transport over rough ground. In addition, the very driving of the steel tube into the ground is time-consuming, which makes the entire prospecting work quite expensive. Furthermore, often a large number of sampling cores of considerable length must be lifted up from the ground without containing any of the substances one hopes to find.
From e.g. the Swiss Patent Specification No. 356 426 is already known a machine comprising a percussion drill which is driven by pressurized air and designed to drive down a drill which is cooled by compressed air, into the section of the ground that is to be prospected. The machine comprises a hood arranged to be applied over the upper end of the drill hole and a pipe connects the hood to a suction fan. A filter is arranged in the pipe and at least a portion of the dust-laden air ascending up the drill hole and collected in the hood is forced to pass through this filter.
The publication is simply concerned with the problems involved in collecting the drill cuttings entrained in the air leaving the drill hole for the purpose of preventing the cuttings from polluting the air around the working area. In order not to overload the centrifugal purification equipment incorporated in the plant a pre-purification unit is arranged in the exhaust pipe. The primary object of this publication thus is to provide a plant that does not pollute the environment.